1. Field of the Invention
The present invention relates to an organopolysiloxane composition with two curing mechanisms, namely photopolymerizability and condensation curability.
2. Description of the Prior Art
The curing of an organopolysiloxane by heating in the presence of an organic peroxide, to produce a silicone rubber elastic body with superior heat resistance, low temperature resistance, weather resistance and electrical characteristics, is well known. Furthermore, ultraviolet light curable organopolysiloxane compositions which are cured by irradiation with light in the presence of a photopolymerization initiator are also known, and examples of such compositions are those disclosed in Japanese Post-Examination Publication (kokoku) No. 52-40334 (JP52-40334B) corresponding to U.S. Pat. No. 4,064,027 and Japanese Laid-open Publication (kokai) No. 60-104158 (JP60-104158A), which incorporate a vinyl group containing polysiloxane and a mercapto group containing polysiloxane, and are cured using a light initiated radical addition reaction. However, these compositions have an odor associated with the mercapto group and are corrosive towards metals, and consequently the uses of such compositions are limited.
Furthermore, additional examples of compositions which undergo curing on light irradiation are the compositions disclosed in Japanese Post-Examination Publication (kokoku) No. 53-36515 (JP53-36515B) corresponding to GB 1323869B and Japanese Laid-open Publication (kokai) No. 60-215009 (JP60-215009A), corresponding to U.S. Pat. No. 4,675,346 which comprise an acryloyl group containing polysiloxane, a photopolymerization initiator and a sensitizer. However, in order to obtain a rubber elastic body, these compositions require the use of high molecular weight linear polymers, and so the relative quantity of acryloyl groups located at the terminals becomes extremely small, resulting in a composition of poor curability, and furthermore the surface portions of the composition in contact with the air undergo almost no curing due to the curing inhibiting effect of oxygen. Consequently, only resin-producing compositions with comparatively large quantities of acryloyl groups were able to be developed, and their cured products were unsatisfactory as rubber elastic bodies.
In order to overcome the drawbacks of the acryloyl group containing polysiloxane compositions described above, adhesives with two curing mechanisms, namely curing due to photopolymerization and curing due to atmospheric moisture (condensation curing), have been proposed and developed. A specific example is the composition disclosed in Japanese Post-Examination Publication (kokoku) No. 6-51774 (JP6-51774B) corresponding to U.S. Pat. No. 4,528,081 which incorporates an organopolysiloxane with an acryloyl group or a methacryloyl group and a hydrolysable group at the terminals, a condensation curing catalyst, and a photopolymerization initiator. However, this composition displays poor adhesiveness to a substrate immediately following irradiation with ultraviolet light, and is consequently difficult to use as an ultraviolet curing adhesive.
In consideration of the circumstances described above, an object of the present invention is to provide an organopolysiloxane composition with two curing mechanisms, namely photopolymerizability and condensation curability, which displays superior adhesiveness, and in particular superior adhesiveness relative to a substrate immediately following irradiation with ultraviolet light.
As a result of intensive investigations of compositions with superior adhesiveness, and in particular superior adhesiveness immediately following irradiation with ultraviolet light, the inventors of the present invention discovered that the reason the composition disclosed in Japanese Post-Examination Publication (kokoku) No. 6-51774 (JP6-51774B) displayed poor adhesiveness relative to a substrate immediately following irradiation with ultraviolet light, was that in one of the curing components of the composition, the part responsible for the photopolymerization, i.e., the acryloyl group or the methacryloyl group, and the part responsible for the condensation curing, i.e., the alkoxy group or the acryloxy group, were bonding together to the same single silicon atom. Consequently in the present invention, the inventors discovered that by using, as one constituent of an organopolysiloxane composition, an organosilicon compound with at least two silicon atoms within a single molecule and with a photopolymerizable group and a condensation curable group bonded to different silicon atoms, the adhesiveness of the composition relative to a substrate immediately following irradiation with ultraviolet light was able to be improved, and as a result were able to complete the present invention.
In other words, the present invention provides an organopolysiloxane composition comprising (A) 100 parts by weight of an organopolysiloxane represented by the general formula (1) shown below 
wherein, each R1 represents, independently, a substituted or unsubstituted monovalent hydrocarbon group of 1 to 15 carbon atoms, and a represents an integer from 10 to 3000; (B) 0.1 to 30 parts by weight of an organosilicon compound represented by the 
general formula (2) shown below
wherein, each R2 represents, independently, a hydrogen atom, a phenyl group or a halogenated phenyl group, each R3 represents, independently, a hydrogen atom or a methyl group, each R4 represents, independently, a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms, X represents a hydrolysable group, each Z1 represents, independently, xe2x80x94R5xe2x80x94, xe2x80x94R5Oxe2x80x94 or xe2x80x94R5(CH3)2SiOxe2x80x94 where each R5 represents, independently, a substituted or unsubstituted bivalent hydrocarbon group of 1 to 10 carbon atoms, Z2 represents an oxygen atom or a substituted or unsubstituted bivalent hydrocarbon group of 1 to 10 carbon atoms, m represents 0, 1 or 2, and n represents 0, 1 or 2);
(C) an effective quantity of a condensation curing catalyst; and
(D) 0.01 to 10 parts by weight of a photopolymerization initiator.
As follows is a more detailed description of an organopolysiloxane composition according to the present invention.
(A) Organopolysiloxane Represented by the General Formula (1)
In the organopolysiloxane represented by the general formula (1), the R1 groups may be the same or different and each group represents a substituted or unsubstituted monovalent hydrocarbon group of 1 to 15 carbon atoms, and preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and a represents an integer from 10 to 3000, and preferably from 50 to 1800.
In the general formula (1), suitable examples of substituted monovalent hydrocarbon groups represented by the symbol R1 include halogenated alkyl groups, e.g., having 1-6 carbon atoms, such as chloromethyl groups, 2-chloroethyl groups, 2-bromoethyl groups, 1,1-dichloropropyl groups, 3-chloropropyl groups and 3,3,3-trifluoropropyl groups; whereas suitable examples of unsubstituted monovalent hydrocarbon groups include alkyl groups, e.g., having 1-6 carbon atoms, such as methyl groups, ethyl groups, propyl groups, isopropyl groups, butyl groups, isobutyl groups, tert-butyl groups, pentyl groups, hexyl groups, and cyclohexyl groups; alkenyl groups, e.g., having 1-6 carbon atoms, such as vinyl groups and allyl groups; aryl groups, e.g., having 6-10 carbon atoms, such as phenyl groups and tolyl groups; and aralkyl groups, e.g., having 7-10 carbon atoms, such as benzyl groups or phenylethyl groups. Of these groups, substituted or unsubstituted alkyl groups of 1 to 6 carbon atoms or phenyl groups are preferred, and methyl groups, ethyl groups, phenyl groups and 3,3,3-trifluoropropyl groups are particularly desirable.
Specific structural examples of organopolysiloxanes represented by the general formula (1) are shown below, although the present invention is in no way limited to the examples shown. 
wherein, Me represents a methyl group, Et represents an ethyl group, Ph represents a phenyl group, and b, or b and c, each represent, independently, an integer of 10 to 3000. These compounds may be used singularly, or in combinations of two or more compounds.
(B) Organosilicon Compound Represented by the General Formula (2)
The organosilicon compound represented by the general formula (2) should be used in quantities from 0.1 to 30 parts by weight, and preferably from 1 to 20 parts by weight, and even more preferably from 5 to 20 parts by weight, per 100 parts by weight of the organopolysiloxane represented by the general formula (1).
In the organosilicon compound represented by the general formula (2), each R2 represents a hydrogen atom, a phenyl group or a halogenated phenyl group, each R3 represents a hydrogen atom or a methyl group, and each R4 represents a substituted or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms which may be the same or different. Suitable examples of substituted monovalent hydrocarbon groups represented by the symbol R4 include halogen substituted monovalent hydrocarbon groups such as halogenated alkyl groups including chloromethyl groups, 2-chloroethyl groups, 2-bromoethyl groups, 1,1-dichloropropyl groups, 3-chloropropyl groups and 3,3,3-trifluoropropyl groups, whereas suitable examples of unsubstituted monovalent hydrocarbon groups include alkyl groups such as methyl groups, ethyl groups, propyl groups, isopropyl groups, butyl groups, isobutyl groups, tert-butyl groups, pentyl groups, hexyl groups, cyclohexyl groups, octyl groups and decyl groups; alkenyl groups such as vinyl groups and allyl groups; aryl groups such as phenyl groups and tolyl groups; and aralkyl groups such as benzyl groups or phenylethyl groups. Of these groups, substituted or unsubstituted monovalent hydrocarbon groups of 1 to 3 carbon atoms, such as methyl groups, ethyl groups, propyl groups, isopropyl groups, vinyl groups and allyl groups are preferred.
X represents a hydrolysable group, and examples of preferred groups include lower alkoxy groups and lower alkenyloxy groups of 1 to 6 carbon atoms, or more preferably 1 to 4 carbon atoms, including alkoxy groups as methoxy groups, ethoxy groups, propoxy groups, butoxy groups and methoxyethoxy groups, and alkenyloxy groups such as vinyloxy groups, allyloxy groups, propenoxy groups, isopropenoxy groups and butenyloxy groups. Other suitable groups include ketoxime groups such as dimethyl ketoxime groups and methylethyl ketoxime groups, and acyloxy groups such as acetoxy groups.
Z1 represents xe2x80x94R5xe2x80x94, xe2x80x94R5Oxe2x80x94 or xe2x80x94R5(CH3)2SiOxe2x80x94, wherein the R5 groups may be the same or different, and represent a substituted or unsubstituted bivalent hydrocarbon group of 1 to 10 carbon atoms. Examples of substituted bivalent hydrocarbon groups represented by the symbol R5 include halogen substituted alkylene groups such as chloromethylene groups, dichloromethylene groups and chloroethylene groups, whereas examples of unsubstituted bivalent hydrocarbon groups include alkylene groups such as methylene groups, ethylene groups, propylene groups and tetramethylene groups, or arylene groups such as phenylene groups, and of these groups, substituted or unsubstituted bivalent hydrocarbon groups of 1 to 3 carbon atoms are preferred. Z2 represents an oxygen atom or a substituted or unsubstituted bivalent hydrocarbon group of 1 to 10 carbon atoms, and preferably 1 to 3 carbon atoms. Suitable examples of substituted bivalent hydrocarbon groups represented by the symbol Z2 include the same groups described above in relation to the R5 group, and suitable examples of unsubstituted bivalent hydrocarbon groups also include the same groups described above in relation to the R5 group. Moreover, m represents 0, 1 or 2, and n represents 0, 1 or 2.
Specific structural examples of organosilicon compounds represented by the general formula (2) are shown below, although the present invention is in no way limited to the examples shown. 
These compounds may be used singularly, or in combinations of two or more compounds.
An organosilicon compound represented by the general formula (2) can be produced in the manner described below. 
wherein R2, R3, R4, m, n, X and Z1 represent the same as described above, xe2x80x94CH2xe2x80x94CH2xe2x80x94Axe2x80x94 corresponds with xe2x80x94Z2xe2x80x94 in the general formula (2), A represents a single bond or an alkylene group of 1 to 8 carbon atoms, with suitable alkylene groups including methylene groups, ethylene groups and propylene groups.
Furthermore, an organosilicon compound represented by the general formula (2) can also be produced using the method shown below. 
wherein R2, R3, R4, m, n, Z1 and X represent the same as described above.
(C) Condensation Curing Catalyst
The condensation curing catalyst utilizes any typically known condensation curing catalyst, and specific examples of effective materials include organometallic compounds of tin or titanium such as alkyl titanates, organosilicon titanates, and metal carboxylates such as tin octylate and dibutyl tin phthalate; amine salts such as dibutylamine-2-ethylhexoate; as well as other acid catalysts or base catalysts, particularly silanol condensation catalysts such as nitrogen containing compounds with a guanidyl group. In those cases in which the hydrolysable group X of the organosilicon compound represented by the general formula (2) is an alkenoxy group, a nitrogen containing compound with a guanidyl group is particularly desirable. The condensation curing catalyst may utilize a single compound, or a combination of two or more compounds.
The condensation curing catalyst is used in an effective quantity, typically between 0.01 and 10 parts by weight, and preferably from 0.1 to 3 parts by weight, per 100 parts by weight of the organopolysiloxane represented by the general formula (1). At quantities less than 0.01 parts by weight the addition has little effect, whereas at quantities exceeding 10 parts by weight the strength of the produced silicone rubber tends to be poor, and the physical characteristics of the cured product may deteriorate.
(D) Photopolymerization Initiator
Known materials can be used as the photopolymerization initiator, and these materials promote the photopolymerization of (meth)acryloyl groups. Specific examples include acetophenone, propiophenone, benzophenone, xanthone, fluorenone, benzaldehyde, anthraquinone, triphenylamine, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4,4-dimethoxybenzophenone, 4-chloro-4-benzylbenzophenone, 3-chloroxanthone, 3,9-dichloroxanthone, 3-chloro-8-nonylxanthone, benzoin, benzoin methyl ether, benzoin butyl ether, bis(4-dimethylaminophenyl) ketone, benzylmethoxy ketal, 2-chlorothioxanthone, diethylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-(4-(methylthio)phenyl)2-morpholino-1-propane, 2,2-dimethoxy-2-phenylacetophenone and diethoxyacetophenone, and these compounds may be used singularly, or in combinations of two or more compounds.
The quantity of photopolymerization initiator should typically be from 0.01 to 10 parts by weight, and preferably from 0.1 to 3 parts by weight, per 100 parts by weight of the organopolysiloxane represented by the general formula (1). At quantities less than 0.01 parts by weight per 100 parts by weight of the organopolysiloxane represented by the general formula (1) the addition has little effect, whereas at quantities exceeding 10 parts by weight the strength of the produced silicone rubber tends to be poor, and the physical characteristics of the cured product may deteriorate.
Organopolysiloxane Composition
An organopolysiloxane composition of the present invention is obtained by uniformly mixing predetermined quantities of the aforementioned constituents (A) to (D). Furthermore, other additives may also be included in a composition of the present invention, provided such additives do not impair the effects of the present invention. For example, inorganic based fillers which do not inhibit curing by light irradiation may be added to a composition to improve the mechanical properties of the produced silicone rubber elastic body, and moreover thixotropic agents, reagents for improving the heat resistance, coloring agents and adhesion-imparting agents may be added in order to adjust certain properties of a composition.
Uses
A composition of the present invention obtained in the manner described above has two curing mechanisms, namely photopolymerizability and condensation curability, and also incorporates photopolymerizable (meth)acryloxyorganosilyl groups, and so irradiation with ultraviolet light causes the composition to cure easily, and within a short time period of only 1 to 20 seconds, to produce a silicone rubber. Furthermore, a rubber elastic body produced in this manner displays the special characteristics of a silicone rubber such as superior heat resistance, weather resistance and low temperature resistance, and so can be utilized in a wide variety of different fields.
Organopolysiloxane compositions according to the present invention can be utilized in potting or coating for substrates for electrical circuits including, e.g., substrates for vehicle components, substrates for outdoor equipment, various power supply substrates and the like, coating for mobile telephone key pads, and moisture proof adhesives for use around the periphery of liquid crystal displays. Furthermore, the potential uses of these compositions are not limited to those listed here, and also include other uses requiring adhesion, moisture proofing, heat resistance, weather resistance and low temperature resistance.